[KyleGoetz]

I forget the linguistic term, but it basically means you stop all sound and constrict air movement in your mouth and throat.

Essentially, it results in a doubling of the subsequent consonant. For example, your って example, it results in "tte." Assuming your native language is English, it's like changing the "ck" sound in "backer" into the "ck, c" sound of "back, cur!" See how in the first, it's just a quick /k/ sound, but in the second example, you have something like a /k/ sound from "back" followed by a brief stop of all air flowing through your throat and mouth, and then the /k/ sound at the beginning of "cur" again?

That's what it does, but in Japanese.